METHOXALEN, A PSORALEN, IS A PHOTOSENSITISER INCREASING SKIN REACTIVITY TO LONG-WAVE LENGTH ULTRAVIOLET RADIATION, AN EFFECT USED IN PHOTOCHEMOTHERAPY OR PUVA [PSORALEN (P) AND HIGH-INTENSITY LONG-WAVELENGTH UVA IRRADIATION ]. METHOXSALEN BONDS WITH DNA INHIBITING DNA SYNTHESIS AND CELL DIVISION, AND CAN LEAD TO CELL INJURY.